Receiver circuit using nanotube-based switches and logic

ABSTRACT

Receiver circuits using nanotube based switches and logic. Preferably, the circuits are dual-rail (differential). A receiver circuit includes a differential input having a first and second input link, and a differential output having a first and second output link. First, second, third and fourth switching elements each have an input node, an output node, a nanotube channel element, and a control structure disposed in relation to the nanotube channel element to controllably form and unform an electrically conductive channel between said input node and said output node. The receiver circuit can sense small voltage inputs and convert them to larger voltage swings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority under 35U.S.C. § 120 to U.S. patent application Ser. No. 11/033,215, filed onJan. 10, 2005, entitled Receiver Circuit Using Nanotube-Based Switchesand Logic, which claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Pat. Apl. Ser. No. 60/581,075, filed on Jun. 18, 2004,entitled Non-Volatile Carbon Nanotube Logic (NLOGIC) Receiver Circuit,which is incorporated herein by reference in its entirety.

This application is related to the following references:

-   -   U.S. Pat. No. 7,115,960, filed on Aug. 13, 2004, entitled        Nanotube-Based Switching Elements;    -   U.S. Pat. No. 6,990,009, filed on Aug. 13, 2004, entitled        Nanotube-Based Switching Elements With Multiple Controls;    -   U.S. Pat. No. 7,071,023, filed on Aug. 13, 2004, entitled        Nanotube Device Structure And Methods Of Fabrication;    -   U.S. Pat. No. 7,138,832, filed on Aug. 13, 2004, entitled        Nanotube-Based Switching Elements And Logic Circuits;    -   U.S. Pat. No. 7,289,357, filed on Aug. 13, 2004, entitled        Isolation Structure For Deflectable Nanotube Elements;    -   U.S. patent application Ser. No. 11/033,087, filed on Jan. 10,        2005, entitled, Nanotube-Based Transfer Devices and Related        Circuits;    -   U.S. Pat. No. 7,288,970, filed on Jan. 10, 2005, entitled,        Integrated Nanotube and Field Effect Switching Device;    -   U.S. patent application Ser. No. 11/033,213, filed on Jan. 10,        2005, entitled Receiver Circuit Using Nanotube-Based Switches        and Transistors;    -   U.S. Pat. No. 7,164,744, filed on Jan. 10, 2005, entitled,        Nanotube-based Logic Driver Circuits;    -   U.S. Pat. No. 7,161,403, filed on Jan. 10, 2005, entitled,        Storage Elements Using Nanotube Switching Elements;    -   U.S. Pat. No. 7,167,026, filed on Jan. 10, 2005, entitled,        Tri-State Circuit Using Nanotube Switching Elements; and    -   U.S. patent application Ser. No. not yet assigned, filed on date        even herewith, entitled Receiver Circuit Using Nanotube-Based        Switches and Transistors.

BACKGROUND

1. Technical Field

The present application generally relates to nanotube switching circuitsand in particular to nanotube switching circuits used in receivercircuits.

2. Discussion of Related Art

Digital logic circuits are used in personal computers, portableelectronic devices such as personal organizers and calculators,electronic entertainment devices, and in control circuits forappliances, telephone switching systems, automobiles, aircraft and otheritems of manufacture. Early digital logic was constructed out ofdiscrete switching elements composed of individual bipolar transistors.With the invention of the bipolar integrated circuit, large numbers ofindividual switching elements could be combined on a single siliconsubstrate to create complete digital logic circuits such as inverters,NAND gates, NOR gates, flip-flops, adders, etc. However, the density ofbipolar digital integrated circuits is limited by their high powerconsumption and the ability of packaging technology to dissipate theheat produced while the circuits are operating. The availability ofmetal oxide semiconductor (“MOS”) integrated circuits using field effecttransistor (“FET”) switching elements significantly reduces the powerconsumption of digital logic and enables the construction of the highdensity, complex digital circuits used in current technology. Thedensity and operating speed of MOS digital circuits are still limited bythe need to dissipate the heat produced when the device is operating.

Digital logic integrated circuits constructed from bipolar or MOSdevices do not function correctly under conditions of high heat or heavyradiation. Current digital integrated circuits are normally designed tooperate at temperatures less than 100 degrees centigrade and few operateat temperatures over 200 degrees centigrade. In conventional integratedcircuits, the leakage current of the individual switching elements inthe “off” state increases rapidly with temperature. As leakage currentincreases, the operating temperature of the device rises, the powerconsumed by the circuit increases, and the difficulty of discriminatingthe off state from the on state reduces circuit reliability.Conventional digital logic circuits also short internally when subjectedto heavy radiation because the radiation generates electrical currentsinside the semiconductor material. It is possible to manufactureintegrated circuits with special devices and isolation techniques sothat they remain operational when exposed to heavy radiation, but thehigh cost of these devices limits their availability and practicality.In addition, radiation hardened digital circuits exhibit timingdifferences from their normal counterparts, requiring additional designverification to add radiation protection to an existing design.

Integrated circuits constructed from either bipolar or FET switchingelements are volatile. They only maintain their internal logical statewhile power is applied to the device. When power is removed, theinternal state is lost unless some type of non-volatile memory circuit,such as EEPROM (electrically erasable programmable read-only memory), isadded internal or external to the device to maintain the logical state.Even if non-volatile memory is utilized to maintain the logical state,additional circuitry is necessary to transfer the digital logic state tothe memory before power is lost, and to restore the state of theindividual logic circuits when power is restored to the device.Alternative solutions to avoid losing information in volatile digitalcircuits, such as battery backup, also add cost and complexity todigital designs.

Important characteristics for logic circuits in an electronic device arelow cost, high density, low power, and high speed. Resistance toradiation and the ability to function correctly at elevated temperaturesalso expand the applicability of digital logic. Conventional logicsolutions are limited to silicon substrates, but logic circuits built onother substrates would allow logic devices to be integrated directlyinto many manufactured products in a single step, further reducing cost.

Devices have been proposed which use nanoscopic wires, such assingle-walled carbon nanotubes, to form crossbar junctions to serve asmemory cells. (See WO 01/03208, Nanoscopic Wire-Based Devices, Arrays,and Methods of Their Manufacture; and Thomas Rueckes et al., “CarbonNanotube-Based Nonvolatile Random Access Memory for MolecularComputing,” Science, vol. 289, pp. 94-97, 7 Jul. 2000.)

Hereinafter these devices are called nanotube wire crossbar memories(NTWCMs). Under these proposals, individual single-walled nanotube wiressuspended over other wires define memory cells. Electrical signals arewritten to one or both wires to cause them to physically attract orrepel relative to one another. Each physical state (i.e., attracted orrepelled wires) corresponds to an electrical state. Repelled wires arean open circuit junction. Attracted wires are a closed state forming arectified junction. When electrical power is removed from the junction,the wires retain their physical (and thus electrical) state therebyforming a non-volatile memory cell.

U.S. Patent Publication No. 2003-0021966 discloses, among other things,electromechanical circuits, such as memory cells, in which circuitsinclude a structure having electrically conductive traces and supportsextending from a surface of a substrate. Nanotube ribbons that canelectromechanically deform, or switch are suspended by the supports thatcross the electrically conductive traces. Each ribbon comprises one ormore nanotubes. The ribbons are typically formed from selectivelyremoving material from a layer or matted fabric of nanotubes.

For example, as disclosed in U.S. Patent Publication No. 2003-0021966, ananofabric may be patterned into ribbons, and the ribbons can be used asa component to create non-volatile electromechanical memory cells. Theribbon is electromechanically-deflectable in response to electricalstimulus of control traces and/or the ribbon. The deflected, physicalstate of the ribbon may be made to represent a corresponding informationstate. The deflected, physical state has non-volatile properties,meaning the ribbon retains its physical (and therefore informational)state even if power to the memory cell is removed. As explained in U.S.Patent Publication No. 2003-0124325, three-trace architectures may beused for electromechanical memory cells, in which the two of the tracesare electrodes to control the deflection of the ribbon.

The use of an electromechanical bi-stable device for digital informationstorage has also been suggested (c.f. U.S. Pat. No. 4,979,149:Non-volatile memory device including a micro-mechanical storageelement).

The creation and operation of bi-stable, nano-electro-mechanicalswitches based on carbon nanotubes (including mono-layers constructedthereof) and metal electrodes has been detailed in a previous patentapplication of Nantero, Inc. (U.S. Pat. Nos. 6,574,130, 6,643,165,6,706,402; U.S. patent application Ser. Nos. 09/915,093, 10/033,323,10/033,032, 10/128,117, 10/341,005, 10/341,055, 10/341,054, 10/341,130,10/776,059, and 10/776,572, the contents of which are herebyincorporated by reference in their entireties).

SUMMARY

The invention provides receiver circuits using nanotube based switchesand logic.

Under one aspect of the invention, a receiver circuit includes adifferential input having a first and second input link, and adifferential output having a first and second output link. First,second, third and fourth switching elements each have an input node, anoutput node, a nanotube channel element, and a control structuredisposed in relation to the nanotube channel element to controllablyform and unform an electrically conductive channel between said inputnode and said output node. The control structure of the first switchingelement is in electrical communication with the first input link, andthe input node is in electrical communication with a low referencevoltage. The output node is in electrical communication with the firstoutput link. The control structure of the second switching element inelectrical communication with the second input link, and the input nodeis in electrical communication with a low reference voltage, and theoutput node is in electrical communication with the second output link.The output node of the third switching element is in electricalcommunication with the first output link, and the control structure isin electrical communication with the second output link and the inputnode is in electrical communication a high reference voltage. The outputnode of the fourth switching element is in electrical communication withthe second output link, and the control structure is in electricalcommunication with the first output link and the input node is inelectrical communication a high reference voltage.

Under another aspect of the invention, the control structure of thefirst and second switching elements includes a control (set) electrodeand a release electrode, and the first input link is coupled to thecontrol (set) electrode of the first switching element and the releaseelectrode of the second switching element. The second input link iscoupled to the control (set) electrode of the second switching elementand the release electrode of the first switching element.

Under another aspect of the invention, the control structure of thethird and fourth switching elements includes a control (set) electrodeand a release electrode, and the first output link is coupled to thecontrol (set) electrode of the fourth switching element. The secondoutput link is coupled to the control (set) electrode of the thirdswitching element, and the release electrodes of the third and fourthswitching elements are coupled to the high reference voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a receiver circuit according to certain embodiments ofthe invention;

FIGS. 2A-D illustrate nanotube switches as used in certain embodimentsof the invention;

FIGS. 3A-C depict the notation used to describe the nanotube switch andits states; and

FIGS. 4A-B depict the operation of the receiver circuit shown in FIG. 1.

DETAILED DESCRIPTION

Preferred embodiments of the invention provide a receiver circuit thatuses nanotube-based switches. Preferably, the circuits are dual-rail(differential). The receiver circuit can sense small voltage inputs andconvert them to larger voltage swings.

FIG. 1 depicts a preferred receiver circuit 10. As illustrated thereceiver circuit 10 receives differential input signal A_(T) and A_(C)on links 25 and 25′ and provides a differential signal to other logic 45via links 32 and 32′.

Receiver 10 includes non-volatile nanotube switches 15 and 20, andnon-volatile nanotube switch pull-up devices 35 and 40. The outputs 30and 30′ of nanotube switches 15 and 20 are connected to the outputs ofpull-up switches 35 and 40. A_(T) is coupled to the control electrode(more below) of nanotube switch 15 and A_(C) is coupled to the releaseelectrode (more below). A_(C) is coupled to the control electrode ofnanotube switch 20 and A_(T) is coupled to the release electrode. Eachnanotube switch 15 and 20 has its signal electrode (more below) coupledto ground. The outputs 30 and 30′ are cross-coupled to the controlelectrodes of the pull-up switches 35 and 40 as depicted. The releaseelectrodes of each pull-up switch are tied to the nanotube channelelement and signal electrode of the switch, as depicted. The signalelectrode is tied to Vdd in this embodiment. The pull-up switches 35 and40 are sized to be volatile devices.

FIGS. 2A-D depict a preferred nanotube switching element 100 incross-section and layout views and in two informational states. Theseswitches may be used for switches 15 and 20 of FIG. 1. A more detaileddescription of these switches may be found in the related casesidentified and incorporated above. A brief description follows here forconvenience.

FIG. 2A is a cross sectional view of a preferred nanotube switchingelement 100. Nanotube switching element includes a lower portion havingan insulating layer 117, control electrode 111, output electrodes 113c,d. Nanotube switching element further includes an upper portion havingrelease electrode 112, output electrodes 113 a,b, and signal electrodes114 a,b. A nanotube channel element 115 is positioned between and heldby the upper and lower portions.

Release electrode 112 is made of conductive material and is separatedfrom nanotube channel element 115 by an insulating material 119. Thechannel element 115 is separated from the facing surface of insulator119 by a gap height G102.

Output electrodes 113 a,b are made of conductive material and areseparated from nanotube channel element 115 by insulating material 119.

Output electrodes 113 c,d are likewise made of conductive material andare separated from nanotube channel element 115 by a gap height G103.Notice that the output electrodes 113 c,d are not covered by insulator.

Control electrode 111 is made of conductive material and is separatedfrom nanotube channel element 115 by an insulating layer (or film) 118.The channel element 115 is separated from the facing surface ofinsulator 118 by a gap height G104.

Signal electrodes 114 a,b each contact the nanotube channel element 115and can therefore supply whatever signal is on the signal electrode tothe channel element 115. This signal may be a fixed reference signal(e.g., Vdd or Ground) or varying (e.g., a Boolean discrete value signalthat can change). Only one of the electrodes 114 a,b need be connected,but both may be used to reduce effective resistance.

Nanotube channel element 115 is a lithographically-defined article madefrom a porous fabric of nanotubes (more below). It is electricallyconnected to signal electrodes 114 a,b. The electrodes 114 a,b andsupport 116 pinch or hold the channel element 115 at either end, and itis suspended in the middle in spaced relation to the output electrodes113 a-d and the control electrode 111 and release electrode 112. Thespaced relationship is defined by the gap heights G102-G104 identifiedabove. For certain embodiments, the length of the suspended portion ofchannel element 115 is about 300 to 350 nm.

Under certain embodiments the gaps G103, G104, G102 are in the range of5-30 nm. The dielectric on terminals 112, 111, and 113 a and 113 b arein the range of 5-30 nm, for example. The carbon nanotube fabric densityis approximately 10 nanotubes per 0.2×0.2 um area, for example. Thesuspended length of the nanotube channel element is in the range of 300to 350 nm, for example. The suspended length to gap ratio is about 5 to15 to 1 for non-volatile devices, and less than 5 for volatileoperation, for example.

FIG. 2B is a plan view or layout of nanotube switching element 100. Asshown in this figure, electrodes 113 b,d are electrically connected asdepicted by the notation ‘X’ and item 102. Likewise electrodes 113 a,care connected as depicted by the ‘X’. In preferred embodiments theelectrodes are further connected by connection 120. All of the outputelectrodes collectively form an output node 113 of the switching element100.

Under preferred embodiments, the nanotube switching element 100 of FIGS.2A and 2B operates as shown in FIGS. 2C and D. Specifically, nanotubeswitching element 100 is in an OPEN (OFF) state when nanotube channelelement is in position 122 of FIG. 1C. In such state, the channelelement 115 is drawn into mechanical contact with dielectric layer 119via electrostatic forces created by the potential difference betweenelectrode 112 and channel element 115. Output electrodes 113 a,b are inmechanical contact (but not electrical contact) with channel element115. Nanotube switching element 100 is in a CLOSED (ON) state whenchannel element 115 is elongated to position 124 as illustrated in FIG.1D. In such state, the channel element 115 is drawn into mechanicalcontact with dielectric layer 118 via electrostatic forces created bythe potential difference between electrode 111 and channel element 115.Output electrodes 113 c,d are in mechanical contact and electricalcontact with channel element 115 at regions 126. Consequently, whenchannel element 115 is in position 124, signal electrodes 114 a and 114b are electrically connected with output terminals 113 c,d via channelelement 115, and the signal on electrodes 114 a,b may be transferred viathe channel (including channel element 115) to the output electrodes 113c,d.

By properly tailoring the geometry of nanotube switching element 100,the nanotube switching element 100 may be made to behave as anon-volatile or a volatile switching element. By way of example, thedevice state of FIG. 2D may be made to be non-volatile by properselection of the length of the channel element relative to the gap G104.(The length and gap are two parameters in the restoring force of theelongated, deflected channel element 115.) Length to gap ratios ofgreater than 5 and less than 15 are preferred for non-volatile device;length to gap ratios of less than 5 are preferred for volatile devices.

The nanotube switching element 100 operates in the following way. Ifsignal electrode 114 and control electrode 111 (or 112) have a potentialdifference that is sufficiently large (via respective signals on theelectrodes), the relationship of signals will create an electrostaticforce that is sufficiently large to cause the suspended, nanotubechannel element 115 to deflect into mechanical contact with electrode111 (or 112). (This aspect of operation is described in the incorporatedpatent references.) This deflection is depicted in FIGS. 2D (and 2C).The attractive force stretches and deflects the nanotube fabric ofchannel element 115 until it contacts the insulated region 118 of theelectrode 111. The nanotube channel element is thereby strained, andthere is a restoring tensil force, dependent on the geometricalrelationship of the circuit, among other things.

By using appropriate geometries of components, the switching element 100then attains the closed, conductive state of FIG. 1D in which thenanotube channel 115 mechanically contacts the control electrode 111 andalso output electrode 113 c,d. Since the control electrode 111 iscovered with insulator 118 any signal on electrode 114 is transferredfrom the electrode 114 to the output electrode 113 via the nanotubechannel element 115. The signal on electrode 114 may be a varyingsignal, a fixed signal, a reference signal, a power supply line, orground line. The channel formation is controlled via the signal appliedto the electrode 111 (or 112). Specifically the signal applied tocontrol electrode 111 needs to be sufficiently different in relation tothe signal on electrode 114 to create the electrostatic force to deflectthe nanotube channel element to cause the channel element 115 to deflectand to form the channel between electrode 114 and output electrode 113,such that switching element 100 is in the CLOSED (ON) state.

In contrast, if the relationship of signals on the electrode 114 andcontrol electrode 111 is insufficiently different, then the nanotubechannel element 115 is not deflected and no conductive channel is formedto the output electrode 113. Instead, the channel element 115 isattracted to and physically contacts the insulation layer on releaseelectrode 112. This OPEN (OFF) state is shown in FIG. 2C. The nanotubechannel element 115 has the signal from electrode 114 but this signal isnot transferred to the output node 113. Instead, the state of the outputnode 113 depends on whatever circuitry it is connected to and the stateof such circuitry. The state of output node 113 in this regard isindependent of channel element voltage from signal electrode 114 andnanotube channel element 115 when the switching element 100 is in theOPEN (OFF) state.

If the voltage difference between the control electrode 111 (or 112) andthe channel element 115 is removed, the channel element 115 returns tothe non-elongated state (see FIG. 2A) if the switching element 100 isdesigned to operate in the volatile mode, and the electrical connectionor path between the electrode 115 to the output node 113 is opened.

Preferably, if the switching element 100 is designed to operate in thenon-volatile mode, the channel element is not operated in a manner toattain the state of FIG. 1A. Instead, the electrodes 111 and 112 areexpected to be operated so that the channel element 115 will either bein the state of FIG. 2C or 2D.

The output node 113 is constructed to include an isolation structure inwhich the operation of the channel element 115 and thereby the formationof the channel is invariant to the state of the output node 113. Sincein the preferred embodiment the channel element is electromechanicallydeflectable in response to electrostatically attractive forces, anoutput node 113 in principle could have any potential. Consequently, thepotential on an output node may be sufficiently different in relation tothe state of the channel element 115 that it would cause deflection ofthe channel element 115 and disturb the operation of the switchingelement 100 and its channel formation; that is, the channel formationwould depend on the state of the output node. In the preferredembodiment this problem is addressed with an output node that includesan isolation structure to prevent such disturbances from being caused.

Specifically, the nanotube channel element 115 is disposed between twooppositely disposed electrodes 113 b,d (and also 113 a,c) of equalpotential. Consequently, there are equal but opposing electrostaticforces that result from the voltage on the output node. Because of theequal and opposing electrostatic forces, the state of output node 113cannot cause the nanotube channel element 115 to deflect regardless ofthe voltages on output node 113 and nanotube channel element 115. Thus,the operation and formation of the channel is made invariant to thestate of the output node.

Under certain embodiments of the invention, the nanotube switchingelement 100 of FIG. 2A may be used as pull-up and pull-down devices toform power-efficient circuits. Unlike MOS and other forms of circuits,the pull-up and pull down devices may be identical devices and need nothave different sizes or materials. To facilitate the description of suchcircuits and to avoid the complexity of the layout and physical diagramsof FIGS. 1A-D, a schematic representation has been developed to depictthe switching elements.

FIG. 3A is a schematic representation of a nanotube switching element100 of FIG. 2A. The nodes use the same reference numerals. The nanotubeswitching element 100 may be designed to operate in the volatile ornon-volatile switching mode. In this example, a non-volatile switchingmode is used as illustrated by switches 15 and 20 in FIG. 1.

FIGS. 3B-C depict a nanotube channel element 100 when its signalelectrodes is tied to ground, and its states of operation. For example,FIG. 3B is a schematic representation of the nanotube switching elementin the OPEN (OFF) state illustrated in FIG. 2C, in which node 114 andthe nanotube channel element 115 are at ground, the control electrode111 is at ground, and the release electrode 112 is at Vdd. The nanotubechannel element is not in electrical contact with output node 113, butinstead is depicted by the short black line 203 representing thenanotube element contacting insulator 119. FIG. 3C is a schematicrepresentation of the switching element in the CLOSED (ON) stateillustrated in FIG. 2D. In this case, signal node 114 and the nanotubechannel element 115 are at ground, the control electrode 111 is at Vdd,and the release electrode 112 is at ground. The nanotube channel elementis deflected into mechanical and electrical contact with the output node113. Moreover, if as described above, geometries are selectedappropriately, the contact will be non-volatile as a result of the Vander Waals forces between the channel element and the uninsulated, outputelectrode.) The state of electrical contact is depicted by the shortblack line 204 representing the nanotube channel element contacting theoutput terminal 113. This results in the output node 113 assuming thesame signal (i.e., Vdd) as the nanotube channel element 115 and signalnode 114. The switches 15 and 20 operate analogously but opposite whenthe signal electrode is tied to Vdd.

FIG. 3A′ is a schematic representation of a nanotube switching element100 of FIG. 2A designed to be used in a volatile operating mode withrelease electrode connected to the nanotube switching element throughthe switching node contacting the nanotube element as illustrated byswitches 35 and 40 in FIG. 1. The nodes use the same reference numeralsplus a prime (′). Also, the release electrode is electrically connectedto the nanotube contact such that there is no voltage difference betweenrelease electrode and the nanotube channel element. The arrow is used toshow the mechanical force and direction on the nanotube channel element115. For example, as depicted, the channel element has a bias away fromelectrode 111, i.e., if the channel element 115 were deflected intocontact with electrode 111 a mechanical restoring force would be in thedirection of the arrow.

FIGS. 3B′-C′ depict a nanotube channel element 100 when its signalelectrodes are tied to VDD, and its states of operation. For example,FIG. 3B′ is a schematic representation of the nanotube switching elementin the OPEN (OFF) state illustrated in FIG. 2C, in which node 114′ andthe nanotube channel element 115′ are at VDD, the release electrode 112′is electrically connected to node 114′ and is therefore also at VDD, andthe control electrode 111′ is also at VDD. The nanotube channel elementis not in electrical contact with output node 113, but instead is in anon-extended position, restored by the mechanical restoring forceindicated by the arrow in FIG. 2B′. FIG. 3C′ is a schematicrepresentation of the switching element in the CLOSED (ON) stateillustrated in FIG. 2D. In this case, signal node 114′ and the nanotubechannel element 115′ are at VDD, the release electrode 112′ iselectrically connected to signal node 114′ and is therefore also at VDD,and the control electrode 111′ is at ground. The nanotube channelelement is deflected into mechanical and electrical contact with theoutput node 113. Moreover, if as described above, geometries areselected appropriately, the contact will be volatile and the channelelement will remain in contact with the uninsulated output electrodeuntil the electrostatic force is removed, and then the mechanicalrestoring force in the direction of the arrow will overcome the van derWaals forces and release nanotube channel element from contact with theoutput electrode. The state of the volatile electrical contact isdepicted by the short black line 204′ representing the nanotube channelelement contacting the output terminal 113′. This results in the outputnode 113′ assuming the same signal (i.e., Vdd) as the nanotube channelelement 115′ and signal node 114′. The switches 35 and 40 operateanalogously but opposite when the signal electrode is tied to ground.

Receiver 10 is designed with non-volatile nanotube switches 15 and 20,and volatile nanotube switches 35 and 40. Non-volatile switches 15 and20 are designed such that the mechanical restoring forces that resultfrom the nanotube elongation after switching are weaker than the van derWaals restraining forces. An electrostatic voltage is used (required) tochange the state of the nanotube from “ON” (CLOSED) to “OFF” (OPEN), and“OFF” to “ON.” Volatile switches 35 and 40 have the release plateelectrically connected to the nanotube contact so that there is noelectrostatic restoring force. Volatile devices 35 and 40 are designedsuch that the mechanical restoring forces that result from the nanotubeelongation after switching are stronger than the van der Waalsrestraining forces, and the volatile nanotube will return to from the“ON” state to the “OFF” state once the electrostatic field is removed(the difference voltage between the input electrode and the nanotubefabric goes to zero). The direction of the mechanical restoring force isindicated by an arrow in the symbol for volatile nanotube switches 35and 40. The nanotube contact of each of the non-volatile switches 15 and20 is connected to ground (reference voltage VREF=0).

FIG. 4A illustrates the operation of receiver 10 shown in FIG. 1 wheninput voltage VAt=VRED, a positive voltage, and complementary voltageVAc=0. VRED is not necessarily the same as VDD, and may be lower thanVDD, for example. The nanotube threshold voltage of nonvolatile nanotubeswitches 15 and 20 is set to activate the switches to the “ON” or “OFF”state in response to voltage VRED. That is, voltage difference of VREDor higher across the control node and nanotube channel element issufficient to make the switch contact the output node and form a channelbetween the signal node and the output node. For the applied conditionsillustrated in FIG. 4A, the voltage difference between the input gateand the nanotube channel element of nonvolatile nanotube switch 15forces the nanotube channel element in contact with the output electrodeand output 30 is thus connected to ground (i.e., the voltage on thesignal electrode of switch 15). Also, the voltage difference betweenrelease gate and the nanotube channel element of nonvolatile nanotubeswitch 20 forces the nanotube channel element in contact with thedielectric layer on the opposing output electrode, and output 30′ is inan open state. If volatile nanotube switch 40 is in the “ON” state atthe time, a current will flow briefly from power supply VDD to groundthrough switches 40 and 15. The resistance RNT of the nanotube channelelement is chosen such that the RNT of switch 15 is substantially lowerthan RNT of switch 40 so that output 30 is held near ground voltage. RNTfor switch 15 is chosen to be 3 to 5 time smaller than RNT for switch40. If switch 40 has a width of 10 parallel carbon nanotubes (NTfibers), then switch 15 is chosen to have a width of 30 to 50 parallelNT fibers, for example. When output 30 is forced to near zero volts, theinput of switch 35 is forced to near zero volts and switch 35 turns“ON.” The input voltage of switch 40 transitions from zero to VDD,reducing the voltage difference between switch 40 input electrode andnanotube element to zero. As the electrostatic force between inputelectrode and nanotube goes to zero, the mechanical restoring forceturns switch 40 “OFF” and current stops through switches 40 and 15.Receiver 10 is in a state 10′ illustrated in FIG. 4B. Logic gates 45input 32 is at zero volts, and input 32′ is at VDD. Output 30′ is atVDD, but no current flows because switch 20 is in the “OFF” (OPEN)position (state).

FIG. 4B illustrates the operation of receiver 10 shown in FIG. 1 wheninput voltage VAt equals zero, and complementary voltage VAc=VRED, apositive voltage. VRED is not necessarily the same as VDD, and may belower than VDD, for example. The nanotube threshold voltage ofnonvolatile nanotube switches 15 and 20 is set to activate the switchesto the “ON” or “OFF” state in response to voltage VRED. For the appliedconditions illustrated in FIG. 4B, the voltage difference between theinput gate and the nanotube fabric of nonvolatile nanotube switch 20forces the nanotube channel element in contact with the outputelectrode, and output 30′ is connected to ground. Also, the voltagedifference between release gate and the nanotube channel element ofnonvolatile nanotube switch 15 forces the nanotube channel element incontact with the dielectric layer on the opposing electrode, and output30 is in an open state. If volatile nanotube switch 35 is in the “ON”state at the time, a current will flow briefly from power supply VDD toground through switches 35 and 20. Nanotube resistance RNT is chosensuch that the RNT of switch 20 is substantially lower than RNT of switch35 so that output 30′ is held near ground voltage. RNT for switch 20 ischosen to be 3 to 5 time smaller than RNT for switch 35. If switch 35has a width of 10 parallel NT fibers, then switch 20 is chosen to have awidth of 30 to 50 parallel NT fibers, for example. When output 30′ isforced to near zero volts, the input of switch 40 is forced to near zerovolts and switch 40 turns “ON.” The input voltage of switch 35transitions from zero to VDD, reducing the voltage difference betweenswitch 35 input electrode and nanotube element to zero. As theelectrostatic force between input electrode and nanotube goes to zero,the mechanical restoring force turns switch 35 “OFF” and current stopsthrough switches 40 and 15. Receiver 10 is in a state 10″ illustrated inFIG. 4B. Logic gates 45 input 32 is at VDD volts, and input 32′ is atzero. Output 30 is at VDD, but no current flows because switch 15 is inthe “OFF” (OPEN) position (state).

Several of the incorporated, related patent references describealternative variations of nanotube-based switches. Many of these may beincorporated into the embodiments described above, providing volatile ornon-volatile behavior, among other things. Likewise the fabricationtechniques taught in such cases may be utilized here as well.

Nanotube-based logic may be used in conjunction with and in the absenceof diodes, resistors and transistors or as part of or a replacement toCMOS, biCMOS, bipolar and other transistor level technologies. Also, thenon-volatile flip flop may be substituted for an SRAM flip flop tocreate a NRAM cell. The interconnect wiring used to interconnect thenanotube device terminals may be conventional wiring such as AlCu, W, orCu wiring with appropriate insulating layers such as SiO2, polyimide,etc, or may be single or multi-wall nanotubes used for wiring.

There is no significant leakage current between input and outputterminals in the “OFF” state of the nanotube-based switch, and there isno junction leakage. Therefore the nanotube-based switch may operate inharsh environments such as elevated temperatures, e.g., 150 to 200deg-C. or higher. There is no alpha particle sensitivity.

While single walled carbon nanotubes are preferred, multi-walled carbonnanotubes may be used. Also nanotubes may be used in conjunction withnanowires. Nanowires as mentioned herein is meant to mean singlenanowires, aggregates of non-woven nanowires, nanoclusters, nanowiresentangled with nanotubes comprising a nanofabric, mattes of nanowires,etc. The invention relates to the generation of nanoscopic conductiveelements used for any electronic application.

The following patent references refer to various techniques for creatingnanotube fabric articles and switches and are assigned to the assigneeof this application. Each is hereby incorporated by reference in theirentirety:

-   -   U.S. patent application Ser. No. 10/341,005, filed on Jan. 13,        2003, entitled Methods of Making Carbon Nanotube Films, Layers,        Fabrics, Ribbons, Elements and Articles;    -   U.S. patent application Ser. No. 09/915,093, filed on Jul. 25,        2001, entitled Electromechanical Memory Array Using Nanotube        Ribbons and Method for Making Same;    -   U.S. patent application Ser. No. 10/033,032, filed on Dec. 28,        2001, entitled Methods of Making Electromechanical Three-Trace        Junction Devices;    -   U.S. patent application Ser. No. 10/033,323, filed on Dec. 28,        2001, entitled Electromechanical Three-Trace Junction Devices;    -   U.S. patent application Ser. No. 10/128,117, filed on Apr. 23,        2002, entitled Methods of NTFilms and Articles; U.S. patent        application Ser. No. 10/341,055, filed Jan. 13, 2003, entitled        Methods of Using Thin Metal Layers to Make Carbon Nanotube        Films, Layers, Fabrics, Ribbons, Elements and Articles;    -   U.S. patent application Ser. No. 10/341,054, filed Jan. 13,        2003, entitled Methods of Using Pre-formed Nanotubes to Make        Carbon Nanotube Films, Layers, Fabrics, Ribbons, Elements and        Articles;    -   U.S. patent application Ser. No. 10/341,130, filed Jan. 13,        2003, entitled Carbon Nanotube Films, Layers, Fabrics, Ribbons,        Elements and Articles;    -   U.S. patent application Ser. No. 10/776,059, filed Feb. 11,        2004, entitled Devices Having Horizontally-Disposed Nanofabric        Articles and Methods of Making The Same; and    -   U.S. patent application Ser. No. 10/776,572, filed Feb. 11,        2004, entitled Devices Having Vertically-Disposed Nanofabric        Articles and Methods of Making the Same.

Volatile and non-volatile switches, and switching elements of numeroustypes of devices, can be thus created. In certain preferred embodiments,the articles include substantially a monolayer of carbon nanotubes. Incertain embodiments the nanotubes are preferred to be single-walledcarbon nanotubes. Such nanotubes can be tuned to have a resistancebetween 0.2-100 kOhm/□ or in some cases from 100 kOhm/□ to 1 GOhm/□.

The receiver circuit facilitates compatibility between carbon nanotubelogic circuits and CMOS logic. For example, the output of conventionalCMOS circuits may drive nanotube-based switches. Dual-rail(differential) logic inputs are used and the receiver circuit mayoperate in a differential sensing mode, at smaller voltage swings forhigh speed and lower power dissipation, with no internal logic referencelevel needed at the receiving end. The output of the receiver circuit isa voltage selected for desired (e.g., optimum) on chip circuitoperation. Consequently, the receiver circuit may operate at a differentvoltage than CMOS logic circuits. Preferred receiver circuits enable ananotube logic chip or an embedded nanotube logic function using onlynanotube logic to interface directly with CMOS circuits driving thereceiver inputs, with input voltage signals that may be different fromon chip voltage signals. Also, preferred receiver circuits enablesintegrated logic blocks using CMOS and combined nanotube-based logic andCMOS technologies to operate at different power supply voltages in thesame system on separate chips, or integrated on the same chip. Such areceiver, and other combined circuits, may be used to facilitate theintroduction of nanotube-based logic in a CMOS environment.

The nanotube switching element of preferred embodiments utilizesmultiple controls for the formation and information of the channel. Insome embodiments, the device is sized to create a non-volatile deviceand one of the electrodes may be used to form a channel and the othermay be used to unform a channel. The electrodes may be used asdifferential dual-rail inputs. Alternatively they may be set and used atdifferent times. For example, the control electrode may be used in theform of a clock signal, or the release electrode may be used as a formof clocking signal. Also, the control electrode and release electrodemay be placed at the same voltage, for example, such that the state ofthe nanotube cannot be disturbed by noise sources such as voltage spikeson adjacent wiring nodes.

A FIG. 2 device may be designed to operate as a volatile or non-volatiledevice. In the case of a volatile device, the mechanical restoring forcedue to nanotube elongation is stronger than the van der Waals retainingforce, and the nanotube mechanical contact with a control or releaseelectrode insulator is broken when the electrical field is removed.Typically, nanotube geometrical factors such as suspended length to gapratios of less than 5 to 1 are used for volatile devices. In the case ofa non-volatile device, the mechanical restoring force due to nanotubeelongation is weaker than the van der Waals retaining force, and thenanotube mechanical contact with a control or release electrodeinsulator remains un-broken when the electric field is removed.Typically, nanotube geometrical factors such as suspended length to gapratios of greater than 5 to 1 and less than 15 to 1 are used fornon-volatile devices. An applied electrical field generating anelectromechanical force is required to change the state of the nanotubedevice. Van der Waals forces between nanotubes and metals and insulatorsare a function of the material used in the fabrication nanotubeswitches. By way of example, these include insulators such as silicondioxide and silicon nitride, metals such as tungsten, aluminum, copper,nickel, palladium, and semiconductors such as silicon. For the samesurface area, forces will vary by less than 5% for some combinations ofmaterials, or may exceed 2× for other combinations of materials, so thatthe volatile and non-volatile operation is determined by geometricalfactors such as suspended length and gap dimensions and materialsselected. It is, however, possible to design devices by choosing bothgeometrical size and materials that exhibit stronger or weaker van derWaals forces. By way of example, nanotube suspended length and gapheight and fabric layer density, control electrode length, width, anddielectric layer thickness may be varied. Output electrode size andspacing to nanotube may be varied as well. Also, a layer specificallydesigned to increase van der Waals forces (not shown) may be addedduring the fabrication nanotube switching element 100 illustrated inFIG. 1. For example, a thin (5 to 10 nm, for example) layer of metal(not electrically connected), semiconductor (not electricallyconnected), or insulating material may be added (not shown) on theinsulator layer associated with control electrode 111 or releaseelectrode 112 that increases the van der Waals retaining force withoutsubstantial changes to device structure for better non-volatileoperation. In this way, both geometrical sizing and material selectionare used to optimize device operation, in this example to optimizenon-volatile operation.

In a complementary circuit such as an inverter using two nanotubeswitching elements 100 with connected output terminals, there can bemomentary current flow between power supply and ground in the invertercircuit as the inverter changes from one logic state to another logicstate. In CMOS, this occurs when both PFET and NFET are momentarily ON,both conducting during logic state transition and is sometimes referredto as “shoot-through” current. In the case of electromechanicalinverters, a momentary current may occur during change of logic state ifthe nanotube fabric of a first nanotube switch makes conductive contactwith the first output structure before the nanotube fabric of a secondnanotube switch releases conductive contact with the second outputstructure. If, however, the first nanotube switch breaks contact betweenthe first nanotube fabric and the first output electrode before thesecond nanotube switch makes contact between the second nanotube fabricand the second output electrode, then a break-before-make inverteroperation occurs and “shoot-through” current is minimized or eliminated.Electromechanical devices that favor break-before-make operation may bedesigned with different gap heights above and below the nanotubeswitching element, for example, such that forces exerted on the nanotubeswitching element by control and release electrodes are different;and/or travel distance for the nanotube switching element are differentin one direction than another; and/or materials are selected (and/oradded) to increase the van der Waals forces in one switching directionand weakening van der Waals forces in the opposite direction.

By way of example, nanotube switching element 100 illustrated in FIG. 1may be designed such that gap G102 is substantially smaller (50%smaller, for example) than gap G104. Also, gap G103 is made bigger suchthat nanotube element 115 contact is delayed when switching. Also,dielectric thicknesses and dielectric constants may be different suchthat for the same applied voltage differences, the electric fieldbetween release electrode 112 and nanotube element 115 is stronger thanthe electric field between control electrode 111 and nanotube element115, for example, to more quickly disconnect nanotube element 115 fromoutput terminals 113 c and 113 d. Output electrodes 113 c and 113 d maybe designed to have a small radius and therefore a smaller contact areain a region of contact with nanotube element 115 compared with the size(area) of contact between nanotube element 115 and the insulator oncontrol terminal 111 to facilitate release of contact between nanotubeelement 115 and output electrodes 113 c and 113 d. The material used forelectrodes 113 c and 113 d may be selected to have weaker van der Waalsforces respect to nanotube element 115 than the van der Waals forcesbetween nanotube element 115 and the insulator on release electrode 112,for example. These, and other approaches, may be used to design ananotube switching element that favors make-before-break operation thusminimizing or eliminating “shoot-through” current as circuits such asinverters switch from one logic state to another.

The material used in the fabrication of the electrodes and contacts usedin the nanotube switches is dependent upon the specific application,i.e. there is no specific metal necessary for the operation of thepresent invention.

Nanotubes can be functionalized with planar conjugated hydrocarbons suchas pyrenes which may then aid in enhancing the internal adhesion betweennanotubes within the ribbons. The surface of the nanotubes can bederivatized to create a more hydrophobic or hydrophilic environment topromote better adhesion of the nanotube fabric to the underlyingelectrode surface. Specifically, functionalization of a wafer/substratesurface involves “derivitizing” the surface of the substrate. Forexample, one could chemically convert a hydrophilic to hydrophobic stateor provide functional groups such as amines, carboxylic acids, thiols orsulphonates to alter the surface characteristics of the substrate.Functionalization may include the optional primary step of oxidizing orashing the substrate in oxygen plasma to remove carbon and otherimpurities from the substrate surface and to provide a uniformlyreactive, oxidized surface which is then reacted with a silane. One suchpolymer that may be used is 3-aminopropyltriethoxysilane (APTS). Thesubstrate surface may be derivatized prior to application of a nanotubefabric.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come within the meaning and range of the equivalency ofthe claims are therefore intended to be embraced therein.

1. A voltage translation circuit, comprising: a differential inputhaving a first and second input links; at least one output; a networkcomprising a plurality of nanotube switching elements, each nanotubeswitching element having an input node, output node, and controlstructure, each nanotube switching element responsive to electricalstimulus on the control structure to controllably form and unform anelectrically conductive channel between the input node and the outputnode; at least two of the plurality of nanotube switching elementselectrically disposed between a reference voltage and the first output;at least two of the plurality of nanotube switching elementselectrically disposed between the first and second input links and theat least one output; wherein the network is constructed and arranged totransform electrical stimulus received at the input links to output atthe at least one output in response to said reference voltage and thecontrollable forming and unforming of the electrically conductivechannel in each of said nanotube switching elements.
 2. The voltagetranslation circuit of claim 1, wherein the differential input is inelectrical communication with a first circuit and the at least oneoutput is in electrical communication with a second circuit, the firstcircuit operable at a first voltage level and the second circuitoperable at a second voltage level.
 3. The voltage translation circuitof claim 2, wherein the second voltage level is greater than the firstvoltage level.
 4. The voltage translation circuit of claim 2, wherein again value between the second voltage level and the first voltage levelis proportionate to the reference voltage.
 5. The voltage translationcircuit of claim 1, wherein the input links are in electricalcommunication with a nanotube-based logic circuit and the at least oneoutput is in electrical communication with CMOS logic circuitry.
 6. Thevoltage translation circuit of claim 1, wherein the input links are inelectrical communication with a nanotube-based logic circuit and the atleast one output is in electrical communication with nanotube-basedlogic circuitry.
 7. The voltage translation circuit of claim 1, whereinfor each of the plurality of nanotube switching elements, the conductivechannel is non-volatilely formed and unformed.
 8. The voltagetranslation circuit of claim 1, wherein for each of the at least twonanotube switching elements electrically disposed between the first andsecond input links and the at least one output, the conductive channelis non-volatilely formed and unformed.
 9. The voltage translationcircuit of claim 1, wherein the at least one output comprises adifferential output in electrical communication with a nanotube-basedlogic circuit and the input links are in electrical communication withCMOS logic circuitry.
 10. The voltage translation circuit of claim 9,wherein for one of the at least two nanotube switching elementselectrically disposed between a reference voltage and the differentialoutput, the output node is in electrical communication with a first linkin the differential output, the control structure is in electricalcommunication with a second link in the differential output and theinput node is in electrical communication with the reference voltage.11. The voltage translation circuit of claim 10, wherein for another ofthe at least two nanotube switching elements electrically disposedbetween a reference voltage and the differential output, the output nodeis in electrical communication with the second link, the controlstructure is in electrical communication with the first link, and theinput node is in electrical communication with a high reference voltage.12. The voltage translation circuit of claim 1, wherein for each of theat least two of the plurality of nanotube switching elementselectrically disposed between the first and second input links and theat least one output, the input node is in electrical communication withground.
 13. The voltage translation circuit of claim 12, wherein thefirst input link of the differential input is coupled to the controlelectrode of the first nanotube switching element and the releaseelectrode of the second nanotube switching element and the second inputlink of the differential input is coupled to the control electrode ofthe second nanotube switching element and the release electrode of thefirst nanotube switching element.
 14. The voltage translation circuit ofclaim 12, the output comprising a differential output having first andsecond links, wherein the output nodes of the first and second nanotubeswitching elements are coupled, respectively, to the first and secondlinks.
 15. A power control circuit comprising: a differential inputhaving first and second input links; at least one output incommunication with a network to be controlled; a first and a secondnanotube switching element, each having a control structure inelectrical communication with the input links for switching between aconductive and a non-conductive state, each having an output node; athird and a fourth nanotube switching element, each having an input nodein electrical communication with a reference power source and eachhaving an output node in electrical communication with a correspondingone of the first and second nanotube switching elements, each having acontrol structure for switching between a conductive and anon-conductive state; wherein in response to electrical stimulus on thedifferential input and the at least one output, switching the first,second, third, and fourth nanotube switching elements between theconductive and the non-conductive state controls power to the network tobe controlled.
 16. The power control circuit of claim 15, wherein thecontrol structure of each of the third and fourth nanotube switchingelements is in electrical communication with at least one of the inputand output nodes.
 17. The power control circuit of claim 15, wherein thedifferential input is in electrical communication with an input networkof logic elements.
 18. The power control circuit of claim 17, whereinthe input network of logic elements is operable at a first power leveland the network to be controlled is operable at a second power level.19. The power control circuit of claim 17, wherein an informationalstate at the input network of logic elements is substantiallyundisturbed by an informational state at the network to be controlled.20. The power control circuit of claim 18, wherein an informationalstate at the input network of logic elements is substantiallyundisturbed by variations in the second power level.
 21. The powercontrol circuit of claim 18, wherein an informational state at thenetwork to be controlled is substantially undisturbed by variations inthe first power level.
 22. The power control circuit of claim 16,wherein the input links are in electrical communication with ananotube-based logic circuit and the output is in electricalcommunication with CMOS logic circuitry.
 23. The power control circuitof claim 16, wherein the output comprises a differential output inelectrical communication with a nanotube-based logic circuit and theinput links are in electrical communication with CMOS logic circuitry.24. The power control circuit of claim 22, constructed and arranged toreduce power consumed by the CMOS logic circuitry.
 25. A system forcontrolling power distribution in an integrated circuit having aplurality of regions, the system comprising: a power source; a networkof nanotube switching devices electrically disposed between a first ofthe plurality of regions and a second of the plurality of regions, firstand second of the nanotube switching elements in the network each havinga control structure in electrical communication with the first of theplurality of regions and an output node in electrical communication withthe second of the plurality of regions; third and fourth of the nanotubeswitching elements in the network, each having an input node inelectrical communication with the power source and an output node inelectrical communication with the second of the plurality of regions; acontrol structure in electrical communication with the network ofnanotube switching devices, operable to selectively switch each of thenanotube switching devices, thereby forming and unforming anelectrically conductive pathway between the first and the second of theplurality of regions of the integrated circuit to selectively distributepower to said corresponding region.
 26. The system of claim 25, whereinelectrical stimulus on the control structure selectively switches eachof the nanotube switching devices between a conductive and anonconductive state.
 27. The system of claim 26, wherein the electricalstimulus on the control structure comprises a select signal.
 28. Thesystem of claim 26, wherein the conductive and the nonconductive statesof each of the nanotube switching devices are substantially undisturbedby noise voltages on any of the plurality of regions of the integratedcircuit.
 29. The system of claim 25, wherein the first of the pluralityof regions comprises nanotube-based switching logic circuitry, operablein response to differential, dual rail signals.
 30. The system of claim29, wherein the second of the plurality of regions comprises CMOS logiccircuitry, operable in response to the power source and electricalstimulus on the network of nanotube switching devices and the network ofsemiconductor switching devices.
 31. The system of claim 25, wherein thenanotube switching devices are non-volatile
 32. The system of claim 25,wherein each of the third and fourth of the nanotube switching elementsin the network are volatile.
 33. The system of claim 31, wherein thenanotube switching devices control the power source applied to thesecond of the plurality of regions
 34. The system of claim 32, whereinthe nanotube switching devices control the power source applied to thesecond of the plurality of regions
 35. The system of claim 26, whereinthe state of each of the nanotube switching devices is substantiallyunchanged by the application of the power source to and the removal ofthe power source from the system.
 36. The system of claim 35, wherein asystem start-up stage comprises the application of the power source, asystem shut-down stage comprises the removal of the power source andwherein power applied during said system start-up stage is substantiallyequivalent to power applied immediately prior to said system shut-downstage.
 37. A method for controlling power distribution in an integratedcircuit having a plurality of regions, the method comprising: providinga power source; providing a network of nanotube switching deviceselectrically disposed between a first of the plurality of regions and asecond of the plurality of regions, the network comprising: first andsecond of the nanotube switching elements each having a controlstructure in electrical communication with the first of the plurality ofregions and an output node in electrical communication with the secondof the plurality of regions; third and fourth of the nanotube switchingelements, each having an input node in electrical communication with thepower source and an output node in electrical communication with thesecond of the plurality of regions; providing a control structure inelectrical communication with the network of nanotube switching devices,operable to selectively switch each of the nanotube switching devices,thereby forming and unforming an electrically conductive pathway betweenthe first and the second of the plurality of regions of the integratedcircuit to selectively distribute power to said corresponding region.38. The method of claim 37, further comprising providing electricalstimulus on the control structure to selectively switch each of thenanotube switching devices between a conductive and a nonconductivestate.
 39. The method of claim 38, wherein providing electrical stimuluson the control structure comprises providing a select signal tointermittently connect and disconnect power to said correspondingregion.
 40. The method of claim 37, wherein the conductive and thenonconductive states of each of the nanotube switching devices areconstructed and arranged to be substantially undisturbed by noisevoltages on any of the plurality of regions of the integrated circuit.41. The method of claim 37, further comprising providing differential,dual rail signals to operate the first of the plurality of regions,wherein the first of the plurality of regions comprises nanotube-basedswitching logic circuitry.
 42. The method of claim 41, furthercomprising providing electrical stimulus on the network of nanotubeswitching elements to operate the second of the plurality of regions,wherein the second of the plurality of regions comprises CMOS logiccircuitry.
 43. The method of claim 37, wherein the nanotube switchingdevices are non-volatile.
 44. The method of claim 37, wherein each ofthe third and fourth of the nanotube switching elements in the networkare volatile.
 45. The method of claim 43, wherein selectively switchingthe nanotube switching devices control the power source applied to thesecond of the plurality of regions
 46. The method of claim 44, whereinselectively switching the nanotube switching devices control the powersource applied to the second of the plurality of regions
 47. The methodof claim 38, wherein when applying the power source to and removing thepower source from the system, the state of each of the nanotubeswitching elements is substantially unchanged.
 48. The method of claim47, further comprising executing a system start-up stage includingapplying the power source and executing a system shut-down stageincluding removing the power source, wherein power applied whileexecuting said start-up stage is substantially equivalent to powerapplied immediately prior to executing the shut-down stage.
 49. Themethod of claim 49, comprising providing non-volatile retention ofinformation indicating a power state for each of the plurality ofregions.